Question

4. While only 5% of babies have learned to walk by the age of 10 months, 75% have earned to walk by 13 months of age. If the age at which babies develop the ability to walk can be described by a Normal Distribution model, find the mean and standard deviation of the Normal model.

Answer 1

Answer:

Using the def. of standard normal distribution

..........................................(1)

T 11 Z=

at 5% the value of z = -1.64

at 75% the value of z = 0.68

lets put these values in the eq(1)

$-1.64= \frac{x-10}{\sigma} \\ \\ 0.68 = \frac{x-13}{\sigma}$

0r

$-1.64\sigma= x-10 \\ 0.68 \sigma = x-13$

solve these two equation we get the standard deviation

$\sigma = -1.29$ approx 1.29 taking mode value

and X= 12.121 (mean)